# Discover the Power of Perpendicular Lines: Exploring Challenging Theorems and Problems Related to 90-Degree Angles

In geometry, two lines are said to be perpendicular if they intersect at a 90-degree angle. Here are some important concepts related to perpendicular lines in geometry:

1. Perpendicular bisector: A line that intersects a segment at its midpoint and forms a right angle with the segment.

2. Perpendicular lines theorem: If two lines intersect to form a pair of congruent, adjacent angles (i.e. two angles whose measures add up to 90 degrees), then the lines are perpendicular.

3. Slope of perpendicular lines: The slopes of two lines that are perpendicular to each other are negative reciprocals. In other words, if the slope of one line is m, then the slope of a line perpendicular to it is -1/m.

4. Perpendicular planes: In three-dimensional space, two planes are said to be perpendicular if they intersect at a right angle.

5. Pythagorean theorem: The Pythagorean theorem can be used to determine if a triangle is a right triangle, which means that one of its angles is 90 degrees (and therefore, any line segment that is perpendicular to one of its sides will be perpendicular to the other side as well).

Understanding these concepts is essential in solving geometry problems involving perpendicular lines and angles.

Points, Theorems and Problems - Index.
Intersection Point.

Orthic Triangle, Theorems and Problems, Index.

Perpendicular Chords. Index.
Theorems and Problems.

GeoGebra, Dynamic Geometry: Simson Line of a Triangle.
HTML5 Animation for Tablets (iPad, Nexus..)

Meanings and syntactic of 'PERPENDICULAR'.
Created using Wordflex Touch Dictionary for iPad in association with Oxford University Press.

Rectangle. Theorems and Problems Index.

Geometry Problem 1525 and a Thematic Poem.
Unveiling the Secrets of an Equilateral Triangle in Right Triangle Geometry: Finding the Midpoint Distance between Segments.

Geometry Problem 1524 and a Thematic Poem.
Unlock the Mystery of Parallelograms: Discover the Length of Segment between the Intersecting Angle Bisectors.

Geometry Problem 1523 and a Thematic Poem.
Discover How to Calculate the Length of the Altitude in an Isosceles Triangle - Get Expert Geometry Tips Now! .

Geometry Problem 1515 and a Thematic Poem.
Mastering Triangle Distance Calculation: Find the Distance from the Intersection of Medians to an Exterior Line. Difficulty Level: High School.

Geometry Problem 1514 and a Thematic Poem.
Discover the Secret to Finding Distances in Regular Hexagons with Interior Squares. Difficulty Level: High School.

Geometry Problem 1511 and Poem.
Finding the Altitude of an Isosceles Triangle Using Distances from a Point on the Extension of the Base. Difficulty Level: High School.

Geometry Problem 1503.
Triangle, Incircle, Tangent, Congruence, Perpendicular.

Geometry Problem 1502.

Geometry Problem 1501.
Square, Exterior Point, Congruent Angles, Segment, Measurement.

Geometry Problem 1500.
Circle, Perpendicular, Tangent, Secant, Cyclic Quadrilateral, Parallel, Similarity, Measurement.

Geometry Problem 1493.
Four Squares, Parallelogram, Auxiliary Lines.

Geometry Problem 1492.
Right Triangle, Altitude, Incenters, Angle, Measurement.

Geometry Problem 1489.
Right Triangle, Angle Bisectors, Perpendicular, Measurement.

Geometry Problem 1488.
Right Triangle, Altitude, Incircle, Tangent, Measurement.

Geometry Problem 1487.
Right Triangle, Altitude, Incircle, Tangent, Measurement.

Geometry Problem 1486.
Right Triangle, Altitude, Incircle, Tangent, Measurement.

Geometry Problem 1485.
Triangle, Orthocenter, Altitude, Circle, Diameter, Tangent, Measurement.

Geometry Problem 1484.
Right Triangle, Altitude, Incircles, Inradius, Measurement.

Geometry Problem 1483.
Isosceles Right Triangle, Excenter, Perpendicular, Measurement.

Geometry Problem 1482.
Right Triangle, Perpendicular, Double Angle, Measurement.

Dynamic Geometry 1479.
Triangle, Circumcircle, Angle Bisector, Perpendicular Bisector, Chord, Concyclic Points, Parallel Lines,, Step-by-step Illustration. GeoGebra, iPad.

Dynamic Geometry 1476.
Droz-Farny Line Theorem, Triangle, Orthocenter, Perpendicular, Collinear Midpoints, Step-by-step Illustration. GeoGebra, iPad.

Dynamic Geometry 1472.
Cyclic Quadrilateral, Perpendicular Diagonals, Rectangle, Step-by-step Illustration.

Dynamic Geometry 1471.
Equilateral Triangle, Inside/Outside Point, Incenters, Tangency Points, Concurrent Lines, Step-by-step Illustration.

Dynamic Geometry 1469.

Geometry Problem 1459.
Two Triangles, Orthocenter, Midpoint, Perpendicular, Step-by-step Illustration using GeoGebra.

Geometry Problem 1457.
Altitudes, Circles, Similarity, Product of the Inradii Lengths, iPad. Step-by-step illustration using GeoGebra.

Geometry Problem 1456.
Altitudes, Orthic Triangle, Circumcircle, Parallel lines, Similarity, Area, iPad. Step-by-step illustration using GeoGebra.

Geometry Problem 1454.
Intersecting Circles, Perpendicular Lines, Cyclic Quadrilateral, Collinear Points, iPad. Step-by-step illustration using GeoGebra.

Dynamic Geometry 1451.
Orthopole of a Line. Step-by-step illustration using GeoGebra.

Dynamic Geometry 1450.
Ortholine, Steiner Line, Complete Quadrilateral, Collineal Orthocenters. Step-by-step illustration using GeoGebra.

Dynamic Geometry 1449.
Salmon Line. Step-by-step illustration using GeoGebra.

Dynamic Geometry 1448.
Simson Line. Step-by-step illustration using GeoGebra.

Dynamic Geometry Problem 1445.
Van Aubel's theorem, Quadrilateral and Four Squares, Centers. Step-by-step animation using GeoGebra.

Geometry Problem 1443.
Triangle Area, Incenter, Circumcenter, 90 Degree, Perpendicular, One-third Area, Art, Poster, Typography, iPad Apps.

Geometry Problem 1442.
Triangle, Altitudes, Orthocenter, Perpendicular, Congruent Angles, Similarity, Measurement, Art, Poster, Typography, iPad Apps.

Geometry Problem 1441.
Intersecting Circles, Perpendicular Bisector, Parallel Lines, Art, Poster, Typography, iPad Apps.

Geometry Problem 1440.
Intersecting Circles, Perpendicular Bisector, Collinear Points, Art, Poster, Typography, iPad Apps.

Geometry Problem 1439.
Rectangle, Diagonal, Perpendicular, Circles, Areas, Art, Poster, Typography, iPad Apps.

Geometry Problem 1438.
Triangle, Incenter, Centroid, Circumcenter, Parallel, 90 Degree, Art, Poster, Typography, iPad Apps.

Geometry Problem 1419.
Triangle, Altitude, Circumcircle, Incenter, Inradius, Perpendicular, Angle Bisector, Midpoint.

Geometry Problem 1417.
Triangle, Cevian, Circumcircle, Incenter, Perpendicular, Angle Bisector, Tangent Lines, Tangent Circles.

Geometry Problem 1416.
Right Triangle, Altitude, Incircle, Excircle, Tangency Points, 45 Degree Angle.

Geometry Problem 1415.
Right Triangle, Altitude, Incircle, Excircle, Tangency Points, Isosceles Triangle.

Geometry Problem 1414.
Right Triangle, Altitude, Incircle, Excircle, Tangency Points, Isosceles Triangle.

Geometry Problem 1413.
Right Triangle, Incircle, Excircle, Tangency Points, Isosceles Right Triangle.

Geometry Problem 1412.
Right Triangle, Incircle, Excircle, Tangency Points, 45 Degree Angle.

Geometry Problem 1411.
Right Triangle, Incircle, Excircle, Tangency Points, Isosceles Right Triangle.

Geometry Problem 1410.
Right Triangle, Incircle, Excircle, Tangency Points, 45 Degree Angle.

Geometry Problem 1409.
Right Triangle, Incircle, Excircle, Collinear Tangency Points, Collinearity.

Geometry Problem 1408.
Right Triangle, Incircle, Excircle, Incenter, Midpoint, Tangency Point, Collinearity.

Geometry Problem 1407.
Right Triangle, Incircle, Excircle, Collinear Tangency Points, Collinearity.

Geometry Problem 1403.
Quadrilateral, 90 Degree Angle, Perpendicular, Congruence.

Geometry Problem 1401.
Right Triangle with three circles on the sides, Isosceles, Diameter, Center, Tangent, Congruence.

Geometry Problem 1400.
Triangle with three rectangles on the sides, Perpendicular Bisectors, Concurrency.

Geometry Problem 1399.
Triangle, Circumcircle, Perpendiculars, Angles, Congruence, Cyclic Quadrilateral.

Geometry Problem 1398.
Isosceles Triangle, Circle, Radius, Perpendicular, Measurement.

Geometry Problem 1397.
Circle, Diameter, Tangent, Secant, 90 Degrees Angle, Perpendicular, Collinear Points.

Geometry Problem 1396.
Triangle with three rectangles on the sides, Vertices, Perpendicular lines, Concurrency.

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